I. Field of the Invention
The present invention relates generally to steering systems for watercraft, and more particularly to the definition and control of predetermined rudder configurations used in maneuvering watercraft.
II. Description of Prior Art
Flanking rudders, as the term is used herein, are rudders which are located forward of the main thrust producing device(s), typically propellers or "screws," for a particular watercraft. Whether the watercraft includes a single screw or several, it would be common to employ a flanking rudder directly in front of each of the screws. The basic concept of flanking rudders has been understood at least as early as the 1800's when such rudders were used in connection with paddle wheeled steamboats. At the present time, flanking rudders are commonly installed on towboats that push barges on the inland river systems of North and South America. The primary function of flanking rudders is to provide the watercraft with a means of steering as the watercraft travels in reverse. For example, as the screws or other thrust-producing device directs reverse thrust toward the front of the watercraft, the flanking rudders are employed in tandem to steer the watercraft in the desired direction. This is particularly useful in the case of utility boats, such as tug boats, which routinely change from forward and reverse thrust in assisting larger ships, such as oil tankers and cargo ships, into a docking position in a river; with towboats that push barges on inland rivers and coastal waters; and, seagoing vessels.
Although the presence of flanking rudders operating in tandem mode is a significant enhancement to the maneuverability of any of these types of vessels, there are situations where greater control over the operation of the flanking rudders would be highly desirable. For example, in many instances, tug boats must attach to one side of a ship having a deeper draft than the tug boat. When reverse thrust is applied over conventional flanking rudders to pull the larger ship, the thrust is necessarily directed against the hull of the larger ship. The undesirable effect is for the stem of the tug boat to be urged away from the ship, thus losing some control over the larger ship. While lines can be used to tie the tug boat to the larger ship, this is an imperfect solution. Ideally, the flanking rudders would be subject to independent control to allow the innermost flanking rudder to remain parallel to the keel of the ship, while the outermost flanking rudder is used to direct thrust in the desired direction. Also, once independent control of the flanking rudders is implemented, it would be quite useful to operate the flanking rudders in a converging or diverging mode, such that the flanking rudders can be placed in a flared position for braking when the vessel is moving forward or moving astern, and for redirection of thrust. Consequently, the present invention is provided as a solution to the foregoing problems by illustrating a novel flanking rudder steering system capable of being controlled in a variety of predefined operational modes by one or more controlling devices.